Workflow analysis of the hottest twin screw pump

2022-07-28
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Working process analysis of twin screw pump

the screw pump uses the reverse rotation of the screw to suck and discharge liquid. The central screw is an automatic screw, which is driven to reverse by the prime mover. The screws at both ends are driven screws, which rotate in reverse with the automatic screw. The threads of the driving and driven screws are double headed threads

due to the meshing of each screw and the close cooperation between the screw and the inner wall of the liner, one or more sealing spaces will be separated between the suction inlet and discharge outlet of the pump. With the rolling and meshing of the screw, these sealing spaces are continuously formed at the suction end of the pump to seal the liquid in the suction chamber. From the suction chamber, it is better used in the plastic recycling particle industry to move continuously along the axial direction of the screw to the discharge end, so as to continuously discharge the liquid enclosed in each space, just like the scene that a nut is continuously pushed forward when the thread is reversed, This is the basic operating principle of the screw pump

structure diagram and operating principle of the three screw pump

the three screw pump is mainly composed of a bushing (pump cylinder) fixed in the pump body, an automatic screw inserted in the pump cylinder and two driven screws engaged with it. Three intermeshing screws form a sealing cavity in the three screw pump cylinder according to each lead, resulting in the sealing between the suction and discharge ports. During the operation of qucheng pump

three screw pump, because the two driven screws are symmetrically meshed with the automatic screw, the radial force acting on the automatic screw is completely balanced, and the automatic screw does not accept zigzag load. The radial force on the driven screw is supported by the pump cylinder bushing along its entire length. Therefore, there is no need to set another bearing at the outer end, and it basically does not accept zigzag load. During operation, an oil film formed between the outer surface of the screw and the inner wall of the pump cylinder can prevent direct contact between metals and greatly reduce the wear of the screw tooth surface

during the operation of three screw pump, the two ends separately act on the suction and discharge pressure of liquid, so axial thrust shall be generated on the screw. For small pumps with a differential pressure less than 10 KGF/cm2, thrust bearings can be used. In addition, the high-pressure oil is introduced into the bottom of each screw shaft sleeve through the central oil hole of the automatic screw, so that a balanced thrust opposite to the axial thrust direction occurs at the lower end of the screw. Screw pump and other positive displacement pumps, when the pump outlet is completely closed, the pressure in the pump will rise to the dangerous level of pump damage or motor overload. Therefore, it is necessary to set a safety valve at the suction and discharge port of the pump

the shaft seal of three screw pump generally adopts mechanical shaft seal, and different methods can be adopted according to the operating pressure

standard for fire water pump device last

1 Check whether the water pump is in good condition before installation

2. The orientation of the pump unit shall be as close to the water source as possible

3. There are two methods for pump and base device, one is the rigid connection directly installed on the cement foundation, and the other is the flexible connection of jgd shock absorber device

4. The direct device can pad the pump 30-40mm higher on the foundation (ready for filling cement slurry), then calibrate it, put on the anchor bolts, fill cement mortar, calibrate it from the beginning after the cement dries up for 3-5 days, and tighten the nuts of the anchor bolts after the cement dries up completely

5. When installing pipelines, the inlet and outlet pipelines shall have their own supports, and the flange of the pump shall not accept excessive pipeline weight

6. The water pump is used for the occasion with suction head. The end of the water inlet pipe shall be equipped with a bottom valve, and the inlet and outlet pipelines shall not have too many bends. There shall be no water or air leakage together

7 its strength and wear resistance are increased by proper heat treatment process (quenching and tempering, carburizing and quenching, etc.) A filter is installed on the inlet pipeline to prevent impurities from entering the impeller. The effective area of the filter shall be 3-4 times the area of the water inlet pipe to ensure the free dredging of the liquid

8. In order to protect and use conveniently and safely, a regulating valve and a pressure gauge are installed on the inlet and outlet pipelines of the pump respectively, so as to ensure the operation within the additional range and the normal operation and service life of the pump

9. If the inlet needs to be expanded and connected, please select the eccentric reducing pipe joint

starting, operation and parking of the unit

I. starting

1 The pump set is used in the occasion with suction range, that is, when the inlet is negative pressure, water shall be filled into the pipeline or the vacuum pump shall be used to divert water, so that the whole pump and inlet pipeline can be filled with water. Pay attention to the necessity of sealing the inlet pipeline, and there shall be no air leakage to meet the working requirements. (it is forbidden to start without water before starting, and it is necessary to start after water first)

2 Roll the rotor by hand for several circles to make the bearing smooth, and check whether there is any collision between the impeller and the sealing ring in the pump. If it fails to rotate, it should not be started until the cause of the problem is found out

3. Close the gate valve and pressure gauge cock on the outlet pipe to reduce the starting current

4. During the trial start, the rotation direction of the motor shall be the same as that of the arrow on the pump, and the meter cock shall be opened

5. When the rotor reaches normal operation and the pressure gauge shows the pressure, gradually open the outlet gate valve and adjust it to the required working condition

II. Operation

1 When the pump unit is in operation, it is necessary to pay attention to the external reading, try to make the pump operate near the flow head specified on the nameplate, and avoid large flow operation

2. Regularly check the motor current value, which should not exceed the additional current

3. The bearing temperature of the pump set shall not be higher than 75 ℃ and shall not exceed the external temperature by 35 ℃

4. The packing gland of the pump unit shall be loosened at the beginning of operation, and it shall be adjusted to an appropriate level after the graphite or packing is completely expanded

5. If the wearing parts are worn too much, they shall be replaced in time

6. If any abnormality is found, stop the machine immediately to check the cause

III. shutdown

1 Close the gate valve on the water outlet pipeline and the vacuum gauge cock

2. Stop the motor and close the manometer cock

3. In case of cold winter, the liquid in the pump shall be drained to avoid frost cracking

4. If the use is suspended for a long time, the pump shall be disassembled, cleaned, oiled and properly kept

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